Subj : Public Info Statement
To : All
From : Daryl Stout
Date : Mon Feb 25 2019 12:07 am
Public Information Statement
National Weather Service Little Rock AR
600 AM CST Mon Feb 25 2019
...Todays Topic for Severe Weather Awareness Week is Flooding...
The National Weather Service, in cooperation with the Arkansas
Department of Emergency Management, has proclaimed the week of
February 24th through March 2nd as Severe Weather Awareness Week
in Arkansas.
A different topic will be discussed each day, and todays topic is
flooding.
High water usually comes in two phases: flash flooding and river
flooding.
Flash floods usually occur within six hours. The rate of
rainfall exceeds the rate of runoff; that is, rain falls faster
than it can be carried away. Because water has nowhere to go, it
covers roads and fills small streams and creeks.
Flash flooding is usually caused by very slow-moving thunderstorms,
or thunderstorms that repeatedly move over the same areas.
Urban settings are especially prone to flash floods due to large
amounts of concrete and asphalt surfaces that do not allow water to
penetrate into the soil.
Places surrounded by steep, hilly terrain are also susceptible to
flash floods due to rapid runoff /water moving downhill at elevated
speeds/ into streams and creeks.
In the last 30 years, flash flooding was the deadliest thunderstorm
hazard, and caused more fatalities than tornadoes and lightning.
There are an average of 80 to 90 fatalities annually due to flash
floods across the country.
Roughly half of flash flood deaths occur when people try to drive
through flooded areas. Moving water two feet deep is sufficient to
carry away most vehicles, even pickup trucks and sport utility
vehicles.
In 2018, there were two such fatalities in late November. The
victims were in a vehicle in the Harrison /Boone County/ area, and
got swept into a drainage ditch. The incident occurred at night
when it is difficult to recognize the dangers of flash flooding.
The most deadly flash flood event in recorded state history also
occurred after dark. In 2010, the Little Missouri River /a flashy
tributary/ rose more than 20 feet during the predawn hours of June
11th. This was after more than half a foot of rain. Campers at the
Albert Pike Recreation Area /Montgomery County/ were awakened to
raging water, and 20 people drowned.
River flooding is a longer term event than flash flooding, and can
last for several days or even weeks. Water from flash flooding
eventually makes its way into rivers, with excess liquid flowing
into nearby towns, fields, etc.
Rivers are most likely to overflow when the soil is saturated, and
runoff rates are high, and/or water levels are elevated prior to a
heavy rain event.
When rivers spill over, it can be devastating. Water can overtake
homes, businesses, and thousands of acres of cropland.
In 2017, a heavy rain event in late April filled rivers in early
May, and water engulfed more than 950,000 acres of cropland in
eastern Arkansas /in 21 of 75 counties/. Tributaries such as the
Black, White, and Cache Rivers were mostly responsible for the
high water. According to the the University of Arkansas System
Division of Agriculture, flooding resulted in over $175 million
in losses /especially to rice, soybeans, and corn/.
...Flood Safety Rules...
You should know which places in your area are prone to flooding, and
avoid these places in times of rising water.
Do not attempt to cross flowing streams while driving or on foot.
If flood waters are between you and your destination, the National
Weather Service wants you to remember a simple slogan: Turn Around -
Dont Drown.
Outdoor activities are very popular in Arkansas. If you enjoy camping
or similar recreation, be especially careful if you spend the night
near streams. A thunderstorm miles upstream from your location could
produce enough rain to cause flooding, even if it is not raining much
where you are.
Never allow children to play around high water, storm drains, and
culverts.
&&
For a list of all the tornadoes and other significant weather events
that occurred in 2018...
https://www.weather.gov/media/lzk/StormsOf2018.pdf
$$
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